I think I just put the exact same fenders on my trailer.. We had to get a bit creative to get them the flare out a enough to fit over the tires and keep a good space between the tire and the fender.. I think they were like $25 each..
The down size is they are a bit narrow.. It wouldn't be to difficult to buy another set of the fenders, split both sets open and weld 'em together.. Add about 3 more inches and it'd all be good..
As far as the axle.. When ya get ready to replace or rebuild.. These folks can't be beat IMHO.. I just had one custom made up for under $200 shipped.. 3500lb, 6x5.5 hubs, 47" to spring centers, 69" hub face to hub face, ez-lube bearing caps, springs, hangers, u-bolts, etc.. Ordered on a Thursday AM and it was delivered Tuesday afternoon.
http://www.freedomaxle.com/